This disclosure relates to improvements in a roller load support mountable on a load-lifting mast of a forklift truck or other industrial vehicle, for engaging the underside of a load to lift it from a floor or other load-supporting surface.
Previous such roller load supports normally have a longitudinally extending blade-like tapered frame with an upper surface for inserting below the underside of the load. The upper surface has openings through which transversely oriented load-engaging upper rollers are pushed upward by floor-engaging lower rollers to protrude above the upper surface of the frame during the insertion process. The protruding upper rollers separate the underside of the load from the frame's upper surface, to minimize the load's frictional resistance to such insertion and protect the underside of the load from damage due to contact with the frame's upper surface during insertion. Meanwhile, the frictional contact of the lower rollers with the floor during the insertion process causes the lower rollers to rotate which, due to their forceful upward contact with the undersides of the protruding upper rollers, also frictionally causes the upper rollers to rotate in contact with the underside of the load in an opposite rotational direction from the lower rollers, thereby urging the insertion of the frame surface relative to the underside of the load. When the insertion of the frame has been accomplished, subsequent lifting of the frame and load by the lift truck disengages the lower rollers from the floor, allowing both the upper and lower rollers to drop downwardly relative to the frame so that the upper rollers no longer protrude above the upper surface of the frame. This establishes a frictional resistance to relative movement between the underside of the load and the upper surface of the frame, which impedes the load from inadvertently moving longitudinally or laterally on the upper surface while the load is being transported and deposited.
A problem with such previous roller load supports is that the vertical space required to house the upper and lower rollers requires a substantial vertical thickness of the tapered frame. This thickness requirement interferes with the desired optimal blade-like tapered thinness of the frame which would make it more easily insertable beneath loads. Previous attempts to reduce the thickness of the frame have emphasized the use of upper and lower rollers in a complex mixture of nonuniform diameters and spacings which create excessive and confusing variables in the manufacture and maintenance of roller load supports.